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Purpose: To investigate the effect of COVID‐19 home confinement on the efficacy of the interventions for controlling myopia, and to select effective therapies to control myopia during COVID‐19 confinement. Method: Children (n = 164) aged 8–12 years with spherical equivalent refraction of −1.00 to −6.00 diopters were stratified into two age subgroups and randomly allocated into the control, 0.01% atropine, orthokeratology (ortho‐k) and atropine combined ortho‐k (ACO) groups. Axial length (AL) was measured at baseline, 6‐, 12‐, 18‐ and 24‐month visits. The follow‐up spanned the period before the COVID‐19 outbreak, the period of the home confinement, and the period of the school reopening. Hence, the AL change in different periods was collected and compared. Data analysis was performed following the criteria of intention to treat (ITT). Results: All 164 children were involved in the ITT analysis. Compared to control, all interventions can still reduce the AL elongation during the COVID‐19 home confinement period (all p < 0.05). However, the efficacy was compromised: individuals experienced more AL elongation during the COVID‐19 home confinement period in the control, 0.01% atropine and ACO groups (all p < 0.05). Interestingly, in the ortho‐k group, the difference was insignificant (p = 0.178), and the interaction between the intervention type (control vs. ortho‐k) and the confinement severity was significant (p for interaction = 0.041), which is different from the atropine (p for interaction = 0.248) or ACO group (p for interaction = 0.988). These results were stable after being adjusted by other variables based on the multivariable regression model. Conclusion: Ortho‐k was less affected by the COVID‐19 home confinement, which is potentially a better therapy for children in this high‐risk environment. Further investigations are warranted to validate this issue. [ABSTRACT FROM AUTHOR]

This study explores whether children's refractive errors and visual behaviors reverted to pre-COVID-19 levels a year after normal schooling resumed in Hong Kong as well as the impact of corneal and internal astigmatism on refractive astigmatism development. Vision survey data and questionnaire results collected in 2022 (n = 119) and 2020 (n = 173) were compared. Cross-sectional data showed similar proportions of astigmatism (cylindrical power ≥ 0.75 D) in the 2020 (49.1%) and 2022 cohorts (55.5%). Despite a 0.28 D increase in corneal astigmatism, a compensatory 0.24 D increase in internal astigmatism of opposite direction kept refractive astigmatism relatively stable. The questionnaire data showed that children spent an additional 0.5 h/day outdoors on weekends post-resumption of normal schooling but engaged in more near-work activities, especially non-screen near-work, by approximately 1 h/day on both weekdays and weekends. These findings were supported by longitudinal data from 72 children who participated in both surveys. This study highlights the significant role of corneal and internal astigmatism in refractive astigmatism changes. Despite the return to in-person classes, children's total near-work time increased and astigmatism remained high. These findings underscore the need for comprehensive strategies to reduce the high environmental risks for refractive error development in children. [ABSTRACT FROM AUTHOR]

Objective: To characterize and compare the ciliary muscle thickness (CMT) between low and high myopes using swept-source anterior segment optical coherence tomography (AS-OCT). Methods: Forty visually healthy young Chinese adults aged 18–25 years were divided into two groups based on refractive errors: low myopia (n = 20, spherical-equivalent refractive error (SER) between −0.50 D to −3.00 D) and high myopia (n = 20, SER ≤ -6.00 D). Cycloplegic refractions were performed before axial length (AL) and CMT were measured using a partial coherence laser interferometer and an AS-OCT respectively. CMT was measured perpendicularly to the sclera-ciliary muscle interface at 1 mm (CMT_1), 2 mm (CMT_2), and 3 mm (CMT_3) posterior to the scleral spur, and at the location with maximal thickness (CMT_MAX). Results: High myopes demonstrated thicker CMT at 2 mm (CMT_2, p = 0.035) and 3 mm (CMT_3, p = 0.003) posterior to the scleral spur, but thinner maximal CMT (CMT_MAX, p = 0.005) than low myopes. The apical CMT_1 and CMT_MAX were also thinner in high myopes than in low myopes (both p< 0.001). CMT_MAX, apical CMT_1, and apical CMT_MAX correlated directly with SER and inversely with AL; in contrast, CMT_2 and CMT_3 showed inverse correlations with SER but direct correlations with AL. Conclusion: Our findings revealed significant differences in CMT between low and high myopes, with high myopes showing thicker CMT at 2 mm and 3 mm posterior to the scleral spur, but thinner maximal CMT. These results provide new evidence of the potential structural differences in ciliary muscles during myopia development and progression. [ABSTRACT FROM AUTHOR]

Evaluating changes in refractive astigmatism after 'study at home' during the COVID pandemic may shed light on the aetiology of refractive errors. To investigate whether there has been a change in the proportion of astigmatism among primary school children after the school closure period during the COVID-19 pandemic. This observational study compared cross-sectional (2018: n = 112; 2020: n = 173) and longitudinal data (n = 38) collected from two vision screenings, one in 2018 and the other after the school closure period in 2020, in the same primary school for children aged 8–10 years. Non-cycloplegic refraction and axial length were measured using an open‐field auto‐refractometer and IOL Master, respectively. A questionnaire focusing on demographic information, near-work time, and outdoor activities was administered to parents of all participants. While there were no significant differences in age, gender, or monthly family income between the two cohorts, astigmatism proportion (Cyl ≥ 0.75 D) in 2020 was 1.5-fold higher than that in 2018 (49.1% vs. 33.9%). The median cylindrical power was significantly higher in 2020 in older children (9 or 10 years old). More importantly, the children participating in both vision screenings had cylindrical power and J0 astigmatism significantly increased by 0.35 ± 0.40 D and 0.21 ± 0.25 D, respectively. A significant increase in astigmatism (both proportion and magnitude) was found after the school closure period. Further studies are needed to investigate the origin of this increased astigmatism. [ABSTRACT FROM AUTHOR]

Myopia (or "short-sightedness") and astigmatism are major causes of visual impairment worldwide. Significant amounts of astigmatism are frequently observed in infants and have been associated with myopia development. Although it is well established that both myopia and astigmatism are associated with ocular structural changes from anterior to posterior segments, very little is known on how these refractive errors alter retinal functions. This study investigated the effects of experimentally induced myopia and myopic-astigmatism on retinal electrophysiology by using an image-guided, multifocal global flash stimulation in chickens, a widely used animal model for refractive error development. Myopia and myopic-astigmatism were experimentally induced, respectively, by wearing spherical (− 10 D, n = 12) and sphero-cylindrical lenses (− 6.00 DS/− 8.00 DCx90: Hyperopic With-The Rule, H-WTR, n = 15; − 6.00 DS/− 8.00 DCx180: Hyperopic Against-The-Rule, H-ATR, n = 11) monocularly for a week (post-hatching day 5 to 12). An aged-matched control group without any lens treatment provided normal data (n = 12). Multifocal electrophysiological results revealed significant regional variation in the amplitude of induced component (IC) (central greater than peripheral; both p < 0.05) in the normal and H-ATR groups, but not in the – 10 D and H-WTR groups. Most importantly, for the first time, our results showed that both H-WTR and H-ATR groups exhibited a significantly longer implicit time of the inner retinal response at the central region when compared to the normal and – 10 D groups, highlighting a significant role of astigmatism in retinal physiology. [ABSTRACT FROM AUTHOR]

During the COVID-19 pandemic, the Hong Kong Government enforced a "school from home" policy between February and September 2020. This cross-sectional epidemiological study was conducted to investigate the prevalence of astigmatism and visual habits after the home confinement period. Vision screenings were conducted at three local government-funded primary schools in Hong Kong from October 2020 to December 2020. A total of 418 ethnically Chinese primary school children completed the eye examination and returned questionnaires concerning demographic information and visual habits. It was found that 46.5% (95% CI, 41.7–61.4%) of the children aged 8 to 11 years had astigmatism ≥ 0.75 D, which was predominately With-The-Rule astigmatism. The prevalence of astigmatism reported in these children is generally higher than that of studies conducted before COVID. Compared to their non-astigmatic peers, astigmatic children had a longer axial length (p < 0.001) and engaged in fewer outdoor activities (p = 0.04). Multiple linear regression analyses also revealed significant relationships between axial length and both cylindrical error and J0 astigmatism. Due to the high astigmatism prevalence, there is a pressing need for further studies on the long-term impact of the pandemic on children's vision. [ABSTRACT FROM AUTHOR]

Myopia, or short-sightedness, is a highly prevalent refractive disorder in which the eye's focal length is too short for its axial dimension in its relaxed state. High myopia is associated with increased risks of blinding ocular complications and abnormal eye shape. In addition to consistent findings on posterior segment anomalies in high myopia (e.g., scleral remodeling), more recent biometric and biomechanical data in myopic humans and animal models also indicate anterior segment anomalies (e.g., corneal biomechanical properties). Because the cornea is the anterior-most ocular tissue, providing essential refractive power and physiological stability, it is important to understand the biochemical signaling pathway during myopia development. This study first aimed to establish the entire chicken corneal proteome. Then, using the classical form deprivation paradigm to induce high myopia in chicks, state-of-the-art bioinformatics technologies were applied to identify eight differentially expressed proteins in the highly myopic cornea. These results provide strong foundation for future corneal research, especially those using chicken as an animal model for myopia development. [ABSTRACT FROM AUTHOR]

Background/Aims: Smartphone use has become an indispensable part of our daily life. The handy design and powerful processor allow smartphone users to perform diversified tasks even when walking. This study aimed to investigate and compare the optical aftereffect and vergence adaptation of using a smartphone while walking and sitting. Methods: Twenty-nine young healthy adults (aged 19 to 24 years old) with normal binocular and accommodative functions were recruited. Participants were asked to watch a movie for 30 minutes using a smartphone while either walking on a treadmill or sitting on a chair. Corneal aberrations and near heterophoria were measured before and after smartphone use by a corneal topographer and modified Thorington heterophoria test, respectively. Results: Using the smartphone while walking induced a change in corneal H/V astigmatism, becoming 0.11±0.03 μm less negative (two-way ANOVA repeated measures, Bonferroni post-hoc test, p = 0.001). This optical aftereffect was significantly higher than after smartphone use while sitting by 0.10±0.03 μm (paired t-test, p = 0.003). Although smartphone use did not result in a significant change in near heterophoria (Bonferroni post-hoc test, p > 0.15), the vergence adaptation showed relatively more eso- or less exo-deviation by 0.79±0.36Δ in the walking than the sitting condition (paired t-test, p = 0.037). Conclusions: Eyecare practitioners should be cautious of the potential optical after effect and vergence adaptation after prolonged smartphone usage. [ABSTRACT FROM AUTHOR]

It is well-known that correction of blur can improve visual perception. However, it is unclear how the beneficial effect of correction is affected by the regions of correction and the spatial uncertainty introduced by the retinal stimulation. The purpose of this study was two-fold: first, to compare the impacts of blur correction between isoeccentric locations of the visual field; and second, to evaluate the effect of spatial cueing in each corrected location on performing a simple task. Five subjects were asked to complete a simple detection task of a small dark spot stimulus presented randomly at four cardinal retinal locations (eccentricity: 5°) under manipulation of attention via an exogenous cue. Both clear and blurred targets were randomly displayed across the visual field and viewed monocularly through a vision simulator, used to minimize peripheral ocular aberrations. Results confirmed the advantage of clear vs/ blurred images under spatial uncertainty. It was also found that the visual benefit from blur correction is unequal at isoeccentric locations, even for a simple detection task. While manipulation of attention in the presence of spatial uncertainty significantly modulated response time (RT) performance, no differential effect was observed for clear and blurred stimuli, suggesting that attention has only a small effect on the optical benefit for a simple detection task when the display is depleted (no distractor). Those observations highlight the importance of field performance asymmetries in optical interventions and may offer useful implications for the design of extrafoveal refractive correction. Further studies are needed to elucidate how the focus of attention interacts with the perceived gain of vision correction. [ABSTRACT FROM AUTHOR]

Aims/Purpose: Myopia is a leading cause of correctable and preventable vision loss worldwide, but the relationship between myopia development and growth of the anterior segment, particularly the cornea, has not been well established. This study aims to investigate whether experimental induction of myopia influences corneal structures in animals. Methods: Ten chicks were unilaterally form deprived by covering their right eyes with translucent diffusers at post‐hatching day 6 (P6). Refractive state, corneal shape, and ocular axial dimensions were measured at 4‐day intervals until P18 using a Hartinger refractometer, a custom‐made videokeratography system, and an A‐scan ultrasonographer, respectively. Parameters in treated vs control eyes were compared at the end of treatment. Repeated one‐way ANOVA was used for statistical analysis, and all parameters were expressed as mean ± SD. Results: At the end of treatment, form‐deprived eyes were myopic (−29.48 ± 8.26D vs. ‐0.61 ± 0.32D) and axially elongated (11.15 ± 0.55 mm vs. 9.51 ± 0.20 mm). At baseline (P6), treated and fellow contralateral eyes had similar corneal power (132.22 ± 6.37D vs. 132.64 ± 5.48D, p = 0.86) and thickness (167.93 ± 6.80 μm vs. 166.43 ± 7.27 μm, p = 0.63), but at P18 form‐deprived eyes had slower corneal flattening and thickening, resulting in significantly steeper (117.73 ± 5.03D vs. 113.22 ± 3.44D, p < 0.05) and thinner corneas (176.80 ± 7.52 μm vs. 192.35 ± 5.62 μm, p < 0.001) than fellow contralateral eyes. Repeated measures correlation analysis further indicated that axial elongation from P6 to P18 was significantly associated with corneal steepening (rrm = 0.77, p < 0.001) and thinning (rrm = −0.69, p < 0.001). Conclusions: This study provides insights into the impact of form deprivation myopia on corneal structures in juvenile animals. Specifically, the corneas of form‐deprived eyes were steeper and thinner because the natural corneal flattening and thickening processes were decelerated by treatment. Further studies are warranted to reveal the mechanisms responsible for this association between development of refractive error and corneal structure. [ABSTRACT FROM AUTHOR]

The cornea is a soft, transparent, composite organic tissue, which forms the anterior outer coat of the eyeball. Although high myopia is increasing in prevalence worldwide and is known to alter the structure and biomechanical properties of the sclera, remarkably little is known about its impact on the biomechanics of the cornea. We developed and validated a novel optical-coherence-tomography-indentation probe–to measure corneal biomechanical properties in situ, in chicks having experimentally-induced high myopia, while maintaining intraocular pressure at levels covering the physiological range. We found that the cornea of highly myopic chicks was more steeply curved and softer, at all tested intraocular pressures, than that in contralateral, non-myopic eyes, or in age-matched normal, untreated eyes. These results indicate that the biomechanical properties of the cornea are altered in chicks developing experimentally-induced myopia. [ABSTRACT FROM AUTHOR]

Purposes: To evaluate the optical performance of blue-light filtering spectacle lenses and investigate whether a reduction in blue light transmission affects visual performance and sleep quality. Methods: Experiment 1: The relative changes in phototoxicity, scotopic sensitivity, and melatonin suppression of five blue-light filtering plano spectacle lenses were calculated based on their spectral transmittances measured by a spectrophotometer. Experiment 2: A pseudo-randomized controlled study was conducted to evaluate the clinical performance of two blue-light filtering spectacle lenses (BF: blue-filtering anti-reflection coating; BT: brown-tinted) with a regular clear lens (AR) serving as a control. A total of eighty computer users were recruited from two age cohorts (young adults: 18–30 yrs, middle-aged adults: 40–55 yrs). Contrast sensitivity under standard and glare conditions, and colour discrimination were measured using standard clinical tests. After one month of lens wear, subjective ratings of lens performance were collected by questionnaire. Results: All tested blue-light filtering spectacle lenses theoretically reduced the calculated phototoxicity by 10.6% to 23.6%. Although use of the blue-light filters also decreased scotopic sensitivity by 2.4% to 9.6%, and melatonin suppression by 5.8% to 15.0%, over 70% of the participants could not detect these optical changes. Our clinical tests revealed no significant decrease in contrast sensitivity either with (95% confidence intervals [CI]: AR–BT [–0.05, 0.05]; AR–BF [–0.05, 0.06]; BT–BF [–0.06, 0.06]) or without glare (95% CI: AR–BT [–0.01, 0.03]; AR–BF [–0.01, 0.03]; BT–BF [–0.02, 0.02]) and colour discrimination (95% CI: AR–BT [–9.07, 1.02]; AR–BF [–7.06, 4.46]; BT–BF [–3.12, 8.57]). Conclusion: Blue-light filtering spectacle lenses can partially filter high-energy short-wavelength light without substantially degrading visual performance and sleep quality. These lenses may serve as a supplementary option for protecting the retina from potential blue-light hazard. Trial Registration: ClinicalTrials.gov [ABSTRACT FROM AUTHOR]

Purpose: To determine the effects of optically imposed astigmatism on early eye growth in chicks. Methods: 5-day-old (P5) White Leghorn chicks were randomly assigned to either wear, monocularly, a “high magnitude” (H: +4.00DS/-8.00DC) crossed-cylindrical lens oriented at one of four axes (45, 90, 135, and 180; n = 20 in each group), or were left untreated (controls; n = 8). Two additional groups wore a “low magnitude” (L: +2.00DS/−4.00DC) cylindrical lens orientated at either axis 90 or 180 (n = 20 and n = 18, respectively). Refractions were measured at P5 and after 7 days of treatment for all chicks (P12), whereas videokeratography and ex-vivo eyeshape analysis were performed at P12 for a subset of chicks in each group (n = 8). Results: Compared to controls, chicks in the treatment groups developed significant amounts of refractive astigmatism (controls: 0.03±0.22DC; treatment groups: 1.34±0.22DC to 5.51±0.26DC, one-way ANOVAs, p≤0.05) with axes compensatory to those imposed by the cylindrical lenses. H cylindrical lenses induced more refractive astigmatism than L lenses (H90 vs. L90: 5.51±0.26D vs. 4.10±0.16D; H180 vs. L180: 2.84±0.44D vs. 1.34±0.22D, unpaired two-sample t-tests, both p≤0.01); and imposing with-the-rule (H90 and L90) and against-the-rule astigmatisms (H180 and L180) resulted in, respectively, steeper and flatter corneal shape. Both corneal and internal astigmatisms were moderately to strongly correlated with refractive astigmatisms (Pearson’s r: +0.61 to +0.94, all p≤0.001). In addition, the characteristics of astigmatism were significantly correlated with multiple eyeshape parameters at the posterior segments (Pearson’s r: -0.27 to +0.45, all p≤0.05). Conclusions: Chicks showed compensatory ocular changes in response to the astigmatic magnitudes imposed in this study. The correlations of changes in refractive, corneal, and posterior eyeshape indicate the involvement of anterior and posterior ocular segments during the development of astigmatism. [ABSTRACT FROM AUTHOR]

Aluminum alloy (Al6061) is a common material used in the ultraprecision area. It can be machined with a good surface finish by single-point diamond turning (SPDT). Due to the material being relatively soft, it is difficult to apply post-processing techniques such as ultraprecision lapping and ultraprecision polishing, as they may scratch the diamond-turned surface. As a result, a novel low-pressure lapping method was developed by our team to reduce the surface roughness. In this study, a finite element model was developed to simulate the mechanism of this novel lapping technology. The simulation results were compared with the experimental results so as to gain a better understanding of the lapping mechanism. [ABSTRACT FROM AUTHOR]